In active cells, pO_2 may be 10 torr at the cell surface and 1 torr at the mitochondria (the organelles where oxidative metabolism occurs).
A) How does myoglobin (p_50 = 2.8 torr, where p_50 is the partial pressure of oxygen required to 50% saturate myoglobin) facilitate the diffusion of O_2 through these cells? (Myoglobin does not just pick up the O_2 at the cell membrane and carry it over to the mitochondrial membrane.)
B) Active muscles consume O_2 much faster than do other tissues. Would myoglobin also be an effective O_2 - transport protein in other tissues? Explain.

a. Oxygen binds to it when it attains a partial saturation of 0.5

b. Yes.

Explanation:

Myoglobin -  is a small globular protein, containing a heme group, that carries oxygen to muscles.

In this case we see how a specialized oxygen storage

protein, myoglobin, is used to store the oxygen and to facilitate its

diffusion within cells.

a) For oxygen binding in this proteins the KD or the “p50” – the amount of oxygen required to give

a fractional saturation of Y=0.5. In the case of myoglobin, the KD is 2-3 torr. In the case above we have a KD of 2.8 which is sufficient for the fractional saturation binding to be activated.

The fractional saturation seems to be sufficient for a noncooperative binding of O2 to carry oxygen from the capillaries to sites of usage like the mitochondria.

It binds 1 molecule of oxygen molecule per molecule of protein.

b. Myoglobin is an intracellular protein propagated in such a way that it is found in skeletal and cardiac muscle cells and is associated to the transport of oxygen from the cytoplasm to the mitochondria where oxygen is used. It is hence a reliable oxygen depot and transporter.

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